KASAN: use-after-free Read in dmabuffs_dname
Hillf Danton
hdanton at sina.com
Sat Mar 7 12:04:23 UTC 2020
On Fri, 06 Mar 2020 21:41:13 -0800
> syzbot found the following crash on:
>
> HEAD commit: 63623fd4 Merge tag 'for-linus' of git://git.kernel.org/pub..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=11653ac3e00000
> kernel config: https://syzkaller.appspot.com/x/.config?x=9833e26bab355358
> dashboard link: https://syzkaller.appspot.com/bug?extid=3643a18836bce555bff6
> compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> userspace arch: i386
>
> Unfortunately, I don't have any reproducer for this crash yet.
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+3643a18836bce555bff6 at syzkaller.appspotmail.com
>
> ==================================================================
> BUG: KASAN: use-after-free in dmabuffs_dname+0x4f4/0x560 drivers/dma-buf/dma-buf.c:48
> Read of size 8 at addr ffff8880a6b390e8 by task syz-executor.1/2394
>
> CPU: 1 PID: 2394 Comm: syz-executor.1 Not tainted 5.6.0-rc3-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
> __dump_stack lib/dump_stack.c:77 [inline]
> dump_stack+0x197/0x210 lib/dump_stack.c:118
> print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
> __kasan_report.cold+0x1b/0x32 mm/kasan/report.c:506
> kasan_report+0x12/0x20 mm/kasan/common.c:641
> __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:135
> dmabuffs_dname+0x4f4/0x560 drivers/dma-buf/dma-buf.c:48
> tomoyo_realpath_from_path+0x165/0x660 security/tomoyo/realpath.c:259
> tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
> tomoyo_check_open_permission+0x2a3/0x3e0 security/tomoyo/file.c:771
> tomoyo_file_open security/tomoyo/tomoyo.c:319 [inline]
> tomoyo_file_open+0xa9/0xd0 security/tomoyo/tomoyo.c:314
> security_file_open+0x71/0x300 security/security.c:1529
> do_dentry_open+0x37a/0x1380 fs/open.c:784
> vfs_open+0xa0/0xd0 fs/open.c:914
> do_last fs/namei.c:3490 [inline]
> path_openat+0x12ee/0x3490 fs/namei.c:3607
> do_filp_open+0x192/0x260 fs/namei.c:3637
> do_sys_openat2+0x5eb/0x7e0 fs/open.c:1149
> do_sys_open+0xf2/0x180 fs/open.c:1165
> __do_compat_sys_open fs/open.c:1212 [inline]
> __se_compat_sys_open fs/open.c:1210 [inline]
> __ia32_compat_sys_open+0x79/0xb0 fs/open.c:1210
> do_syscall_32_irqs_on arch/x86/entry/common.c:337 [inline]
> do_fast_syscall_32+0x27b/0xe16 arch/x86/entry/common.c:408
> entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
> RIP: 0023:0xf7fd8e39
> Code: 1d 00 00 00 89 d3 5b 5e 5d c3 8b 04 24 c3 8b 1c 24 c3 8b 3c 24 c3 90 90 90 90 90 90 90 90 90 90 90 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90
> RSP: 002b:00000000f5db2014 EFLAGS: 00000296 ORIG_RAX: 0000000000000005
> RAX: ffffffffffffffda RBX: 00000000f5db204c RCX: 0000000000000000
> RDX: 0000000000000000 RSI: 0000000000000c09 RDI: 00000000f5db204c
> RBP: 00000000f5db2168 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
>
> Allocated by task 2388:
> save_stack+0x23/0x90 mm/kasan/common.c:72
> set_track mm/kasan/common.c:80 [inline]
> __kasan_kmalloc mm/kasan/common.c:515 [inline]
> __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:488
> kasan_kmalloc+0x9/0x10 mm/kasan/common.c:529
> __do_kmalloc mm/slab.c:3656 [inline]
> __kmalloc+0x163/0x770 mm/slab.c:3665
> kmalloc include/linux/slab.h:560 [inline]
> kzalloc include/linux/slab.h:669 [inline]
> dma_buf_export+0x24d/0xa80 drivers/dma-buf/dma-buf.c:533
> ion_alloc drivers/staging/android/ion/ion.c:386 [inline]
> ion_ioctl+0x5a9/0xd20 drivers/staging/android/ion/ion.c:495
> compat_ptr_ioctl+0x6e/0xa0 fs/ioctl.c:804
> __do_compat_sys_ioctl fs/ioctl.c:857 [inline]
> __se_compat_sys_ioctl fs/ioctl.c:808 [inline]
> __ia32_compat_sys_ioctl+0x245/0x2c0 fs/ioctl.c:808
> do_syscall_32_irqs_on arch/x86/entry/common.c:337 [inline]
> do_fast_syscall_32+0x27b/0xe16 arch/x86/entry/common.c:408
> entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
>
> Freed by task 2380:
> save_stack+0x23/0x90 mm/kasan/common.c:72
> set_track mm/kasan/common.c:80 [inline]
> kasan_set_free_info mm/kasan/common.c:337 [inline]
> __kasan_slab_free+0x102/0x150 mm/kasan/common.c:476
> kasan_slab_free+0xe/0x10 mm/kasan/common.c:485
> __cache_free mm/slab.c:3426 [inline]
> kfree+0x10a/0x2c0 mm/slab.c:3757
> dma_buf_release+0x343/0x420 drivers/dma-buf/dma-buf.c:111
> __fput+0x2ff/0x890 fs/file_table.c:280
> ____fput+0x16/0x20 fs/file_table.c:313
> task_work_run+0x145/0x1c0 kernel/task_work.c:113
> tracehook_notify_resume include/linux/tracehook.h:188 [inline]
> exit_to_usermode_loop+0x316/0x380 arch/x86/entry/common.c:164
> prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
> syscall_return_slowpath arch/x86/entry/common.c:278 [inline]
> do_syscall_32_irqs_on arch/x86/entry/common.c:352 [inline]
> do_fast_syscall_32+0xbbd/0xe16 arch/x86/entry/common.c:408
> entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
>
> The buggy address belongs to the object at ffff8880a6b39000
> which belongs to the cache kmalloc-1k of size 1024
> The buggy address is located 232 bytes inside of
> 1024-byte region [ffff8880a6b39000, ffff8880a6b39400)
> The buggy address belongs to the page:
> page:ffffea00029ace40 refcount:1 mapcount:0 mapping:ffff8880aa400c40 index:0x0
> flags: 0xfffe0000000200(slab)
> raw: 00fffe0000000200 ffffea0002346b48 ffffea00022f49c8 ffff8880aa400c40
> raw: 0000000000000000 ffff8880a6b39000 0000000100000002 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
> ffff8880a6b38f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff8880a6b39000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >ffff8880a6b39080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ^
> ffff8880a6b39100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8880a6b39180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
Add a completion for dmabuf releaser to wait those who are either
holding the resv lock or aquiring it.
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -334,6 +334,9 @@ struct dma_buf {
__poll_t active;
} cb_excl, cb_shared;
+
+ atomic_t resv_user;
+ struct completion done;
};
/**
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -45,11 +45,20 @@ static char *dmabuffs_dname(struct dentr
size_t ret = 0;
dmabuf = dentry->d_fsdata;
+ if (!dmabuf)
+ goto print_name;
+
+ atomic_inc(&dmabuf->resv_user);
+
dma_resv_lock(dmabuf->resv, NULL);
if (dmabuf->name)
ret = strlcpy(name, dmabuf->name, DMA_BUF_NAME_LEN);
dma_resv_unlock(dmabuf->resv);
+ if (atomic_dec_and_test(&dmabuf->resv_user))
+ complete(&dmabuf->done);
+
+print_name:
return dynamic_dname(dentry, buffer, buflen, "/%s:%s",
dentry->d_name.name, ret > 0 ? name : "");
}
@@ -85,6 +94,10 @@ static int dma_buf_release(struct inode
return -EINVAL;
dmabuf = file->private_data;
+ file->f_path.dentry->d_fsdata = NULL;
+ atomic_inc(&dmabuf->resv_user);
+ if (!atomic_dec_and_test(&dmabuf->resv_user))
+ wait_for_completion(&dmabuf->done);
BUG_ON(dmabuf->vmapping_counter);
@@ -562,6 +575,7 @@ struct dma_buf *dma_buf_export(const str
mutex_init(&dmabuf->lock);
INIT_LIST_HEAD(&dmabuf->attachments);
+ init_completion(&dmabuf->done);
mutex_lock(&db_list.lock);
list_add(&dmabuf->list_node, &db_list.head);
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